[3.12] Fix undefined behaviour in datetime.time.fromisoformat() (GH-111982) (#111992)

miss-islington · Yhg1s · web-flow · commit 1afc4dc3e6b9 · 2023-11-12T00:39:03.000Z
Fix undefined behaviour in datetime.time.fromisoformat() (GH-111982) Fix undefined behaviour in datetime.time.fromisoformat() when parsing a string without a timezone. 'tzoffset' is not assigned to by parse_isoformat_time if it returns 0, but time_fromisoformat then passes tzoffset to another function, which is undefined behaviour (even if the function in question does not use the value). (cherry picked from commit 21615f7) Co-authored-by: T. Wouters <thomas@python.org>
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
@@ -4620,7 +4620,7 @@ time_fromisoformat(PyObject *cls, PyObject *tstr) {
     }
 
     int hour = 0, minute = 0, second = 0, microsecond = 0;
-    int tzoffset, tzimicrosecond = 0;
+    int tzoffset = 0, tzimicrosecond = 0;
     int rv = parse_isoformat_time(p, len,
                                   &hour, &minute, &second, &microsecond,
                                   &tzoffset, &tzimicrosecond);

Original file line number	Diff line number	Diff line change
`@@ -4620,7 +4620,7 @@ time_fromisoformat(PyObject cls, PyObject tstr) {`
`4620`	`4620`	`}`
`4621`	`4621`
`4622`	`4622`	`int hour = 0, minute = 0, second = 0, microsecond = 0;`
`4623`		`- int tzoffset, tzimicrosecond = 0;`
	`4623`	`+ int tzoffset = 0, tzimicrosecond = 0;`
`4624`	`4624`	`int rv = parse_isoformat_time(p, len,`
`4625`	`4625`	`&hour, &minute, &second, &microsecond,`
`4626`	`4626`	`&tzoffset, &tzimicrosecond);`